:root {
  --background-color-light: #f8f9fa;
  --text-color-light: #212529;
  --app-container-bg-light: #ffffff;
  --header-border-light: #dee2e6;
  --project-card-bg-light: #ffffff;
  --project-card-border-light: #e9ecef;
  --text-muted-light: #6c757d;
  --button-bg-light: #007bff;
  --button-text-light: #ffffff;
  --accent-color: #007bff;

  --background-color-dark: #1a1a1a;
  --text-color-dark: #e9ecef;
  --app-container-bg-dark: #212121;
  --header-border-dark: #343a40;
  --project-card-bg-dark: #2c2c2c;
  --project-card-border-dark: #495057;
  --text-muted-dark: #adb5bd;
  --button-bg-dark: #007bff;
  --button-text-dark: #ffffff;
  --input-bg-dark: #3a3a3a;
  --input-border-dark: #495057;
  --input-text-dark: #e9ecef;
}

body {
  font-family: 'Noto Sans KR', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Oxygen, Ubuntu, Cantarell, "Fira Sans", "Droid Sans", "Helvetica Neue", sans-serif;
  margin: 0;
  background-color: var(--background-color-light);
  color: var(--text-color-light);
  transition: background-color 0.3s, color 0.3s;
}

h1, h2, h3, h4, h5, h6, .site-title, .page-header h1 {
    font-family: 'Noto Sans KR', sans-serif;
    font-weight: 700;
}

.app-container {
  max-width: 1140px;
  margin: 0 auto;
  background-color: var(--app-container-bg-light);
  border-radius: 8px;
  box-shadow: 0 4px 6px rgba(0,0,0,0.05);
  overflow: hidden;
}

.site-header {
    border-bottom: 1px solid var(--header-border-light);
}

.page-header {
  text-align: center;
  padding: 60px 20px;
  background: linear-gradient(135deg, #007bff 0%, #0056b3 100%);
  color: white;
}

.page-header h1 {
  margin: 0;
  font-size: 48px;
  font-weight: 700;
  text-shadow: 1px 1px 2px rgba(0,0,0,0.2);
}

.page-header p {
  font-size: 20px;
  color: rgba(255,255,255,0.85);
  font-family: 'Noto Sans KR', sans-serif;
}

.main-content {
  padding: 40px 20px;
}

/* project-nav is now a bootstrap row */
.project-nav {
  gap: 20px;
}

.project-card {
  background-color: var(--project-card-bg-light);
  border: 1px solid var(--project-card-border-light);
  border-radius: 12px;
  padding: 25px;
  text-decoration: none;
  color: var(--text-color-light);
  transition: transform 0.2s, box-shadow 0.2s, border-color 0.2s;
  display: flex;
  flex-direction: column;
  height: 100%;
}

.project-card:hover {
  transform: translateY(-8px);
  box-shadow: 0 8px 25px rgba(0,0,0,0.1);
  border-color: var(--accent-color);
}

.project-card h3 {
  margin-top: 0;
  font-size: 22px;
  color: var(--accent-color);
}

.project-card p {
  font-size: 16px;
  color: var(--text-muted-light);
  flex-grow: 1;
}

/* Responsive Styles */
@media (max-width: 768px) {
  .page-header {
    padding: 40px 15px;
  }

  .page-header h1 {
    font-size: 32px;
  }

  .page-header p {
    font-size: 16px;
  }

  .main-content {
    padding: 25px 15px;
  }

  .project-card {
    padding: 18px;
  }

  .project-card h3 {
    font-size: 19px;
  }

  .project-card p {
    font-size: 14px;
  }

  .app-container {
    border-radius: 0;
  }

  h2 {
    font-size: 1.5rem;
    margin-top: 30px !important;
    margin-bottom: 20px !important;
  }

  /* Bootstrap Overrides for Mobile */
  .display-1 { font-size: 3.5rem; }
  .display-2 { font-size: 3rem; }
  .display-3 { font-size: 2.5rem; }
  .display-4 { font-size: 2rem; }
  
  .lead { font-size: 1.1rem; }
  
  h1 { font-size: 1.8rem; }
  .my-5 { margin-top: 2rem !important; margin-bottom: 2rem !important; }
}

@media (max-width: 480px) {
  .page-header h1 {
    font-size: 28px;
  }

  .project-card {
    padding: 15px;
  }
}

.site-footer {
  text-align: center;
  padding: 30px 20px;
  border-top: 1px solid var(--header-border-light);
  font-size: 14px;
  color: var(--text-muted-light);
}

.footer-links {
  margin-top: 10px;
}

.footer-links a {
  color: var(--text-muted-light);
  text-decoration: none;
  margin: 0 10px;
}

/* Dark Theme Overrides */
body.dark-theme {
  background-color: var(--background-color-dark);
  color: var(--text-color-dark);
}

.dark-theme .app-container {
  background-color: var(--app-container-bg-dark);
}

.dark-theme .site-header,
.dark-theme .site-footer {
  border-color: var(--header-border-dark);
}

.dark-theme .page-header {
    background: linear-gradient(135deg, #232323 0%, #3a3a3a 100%);
    border-color: var(--header-border-dark);
}

.dark-theme h1, .dark-theme h2, .dark-theme h3, .dark-theme h4, .dark-theme h5, .dark-theme h6,
.dark-theme .site-title,
.dark-theme .project-card,
.dark-theme .page-header h1 {
  color: var(--text-color-dark);
}

.dark-theme .page-header p,
.dark-theme .project-card p,
.dark-theme .site-footer,
.dark-theme .footer-links a {
  color: var(--text-muted-dark);
}

.dark-theme .project-card {
  background-color: var(--project-card-bg-dark);
  border-color: var(--project-card-border-dark);
}

.dark-theme .project-card:hover {
  border-color: var(--accent-color);
}

.dark-theme .project-card h3 {
    color: var(--accent-color);
}

.dark-theme .navbar-light .nav-link {
    color: var(--text-color-dark);
}

.dark-theme .navbar-light .navbar-toggler-icon {
    background-image: url("data:image/svg+xml,%3csvg xmlns='http://www.w3.org/2000/svg' width='30' height='30' viewBox='0 0 30 30'%3e%3cpath stroke='rgba(255, 255, 255, 0.8)' stroke-linecap='round' stroke-miterlimit='10' stroke-width='2' d='M4 7h22M4 15h22M4 23h22'/%3e%3c/svg%3e");
}

.dark-theme .blockquote-footer {
    color: var(--text-muted-dark);
}

/* Dark Theme for Forms */
.dark-theme .form-control {
    background-color: var(--input-bg-dark);
    color: var(--input-text-dark);
    border-color: var(--input-border-dark);
}

.dark-theme .form-control:focus {
    background-color: var(--input-bg-dark);
    color: var(--input-text-dark);
    border-color: var(--accent-color);
    box-shadow: 0 0 0 0.2rem rgba(0, 123, 255, 0.25);
}

.dark-theme .list-group-item {
    background-color: var(--project-card-bg-dark);
    border-color: var(--project-card-border-dark);
    color: var(--text-color-dark);
}

.dark-theme .list-group-item:hover {
    background-color: #343a40;
}

.dark-theme .bg-light {
    background-color: var(--project-card-bg-dark) !important;
}

/* Theme Toggle Switch */
.theme-toggle {
  position: relative;
  display: inline-block;
  width: 60px;
  height: 34px;
}

.theme-toggle input {
  opacity: 0;
  width: 0;
  height: 0;
}

.slider {
  position: absolute;
  cursor: pointer;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background-color: #ccc;
  transition: .4s;
  border-radius: 34px;
}

.slider:before {
  position: absolute;
  content: "";
  height: 26px;
  width: 26px;
  left: 4px;
  bottom: 4px;
  background-color: white;
  transition: .4s;
  border-radius: 50%;
}

input:checked + .slider {
  background-color: #007bff;
}

input:checked + .slider:before {
  transform: translateX(26px);
}